An organic EL display device is arranged with a light emitting element in each pixel and an image is displayed by individually controlling the emitted light. A light emitting element includes a structure in which a layer (referred to herein as [light emitting layer]) including an organic EL material is sandwiched between a pair of anodes, one distinguished as an anode and the other as a cathode. When electrons are injected to the light emitting layer from the cathode and holes are injected from the anode, the electrons and hole recombine. Light emitting molecules within the light emitting layer are excited by surplus energy discharged thereby and light is subsequently emitted by de-excitation.
In an organic EL display device, the anode of each light emitting element is arranged as a pixel electrode for each pixel and the cathode is arranged as a common electrode across a plurality of pixels and applied with a common potential. The organic EL display device controls light emission of a pixel by applying the potential of a pixel electrode to each pixel with respect to the potential of the common electrode. Furthermore, the cathode may be arranged in each pixel and in this case it is not necessary that a common potential is applied to all pixels.
However, a light emitting layer of an organic EL display device is easily degraded by the infiltration of water and a problem exists whereby a non-lighting region called a dark spot is produced. In order to solve such a problem, a sealing layer for preventing the infiltration of water is arranged in many organic EL display devices.
For example, an organic light emitting display device is disclosed in Japanese Laid Open Patent Publication No. 2010-027561 arranged with a substrate, a display part formed above the substrate, a sealing film covering the display part and a non-light emitting region of the periphery side of the display part and the density and thickness of which increases from the center part to an edge part. In this way, the lifetime of an organic light emitting display device is increased by preventing water or oxygen from permeating in a side surface direction.
In recent years, flexible display devices are actively being developed in which display regions can be bent. While a sealing layer arranged in a flexible display device has high barrier properties at high densities, cracks may easily occur when a sealing layer is bent. Since cracks which occur in a sealing layer can become a water infiltration path, reliability of a display device drops.